Chemistry · Mole concept, molar mass, percentage composition, empirical and molecular formulae

of chloroplatinic acid of an organic diacidic base left 0.09 g of platinum on ig

\( 0.3 \mathrm{g} \) of chloroplatinic acid of an organic diacidic base left 0.09 g of platinum on ignition. The molecular weight of the organic base is :

  • A. 120
  • B. 240
  • C. 180
  • D. 60

Step-by-step solution

The chloroplatinic acid salt of a diacidic base has formula (BH2)PtCl6. From 0.3 g salt, 0.09 g Pt is obtained, so Pt fraction = 0.09/0.3 = 0.3. Molar mass Pt = 195 g/mol, so molar mass of salt = 195/0.3 = 650 g/mol. Molar mass of H2PtCl6 = 2 + 195 + 6×35.5 = 410 g/mol. Thus molar mass of base = 650 - 410 = 240 g/mol.
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